Precipitation has a great influence on river height, often quickly.

Precipitation influences streamflow

On Dec. 24, 2002, about two inches of rainfall fell in the Peachtree Creek watershed. This provides a good example to describe streamflow characteristics during a storm since the rain fell for only a few hours on that day and Peachtree Creek was at base-flow conditions before the rain started. The chart below shows rainfall, in inches, during each 15-minute increment on Dec. 24^th and the continuous measure of streamflow, in cubic feet per second (ft³/s).

The brown line in the chart shows that streamflow is much higher during the flood period than just before it. The line shows that the baseflow was about 50 ft³/s before the river started to rise, but that just a few hours later, at 9:00 AM streamflow was over 6, 000 ft³/s - that is about 150 times the amount of water flowing by as during baseflow conditions. This is characteristic of small streams, especially urban streams where runoff enters the river very quickly.